Canada has responded that it is “seriously concerned” with Saudi Arabia’s escalation of the matter.

Saudi Arabia’s national airline Saudia suspended flights to and from Toronto in an escalating feud with Canada over the arrest of several prominent human-rights activists.

Saudia announced on Twitter Monday evening that it would be suspending inbound and outbound flights to Toronto Pearson International Airport beginning August 13. Toronto was previously the only Canadian destination Saudia served.

The sudden announcement prompted concern among passengers travelling to and from Canada.

Dear guest, all flights from or to Canada will be suspended from 13th august However the penalties and fees will be temporarily canceled from 6th august. Thank you

Others asked about the influx of North American travellers with planned trips to Mecca for the annual Hajj pilgrimage, which begins next week. More than 2.4 million worshippers descended onto the Islamic holy site in 2017, and millions are expected this year.

In response, Saudia promised to waive penalties and fees temporarily beginning on Monday for all upcoming direct flights to or from Toronto. The airline added that it was working to find alternate solutions to the issue.

Among the women recently arrested is Samar Badawi, an award-winning women’s rights activist who has fought to abolish the country’s patriarchal male guardianship laws, and who is also the sister of jailed human-rights blogger Raif Badawi.

“The Kingdom views the Canadian position as an affront to the Kingdom that requires a sharp response to prevent any party from attempting to meddle with Saudi sovereignty,” the Saudi foreign ministry said in a statement.

In the first public response to Saudi Arabia’s escalation, Canada’s foreign minister Chrystia Freeland said Canada was “seriously concerned” about the Kindom’s actions, and is “seeking greater clarity.”

“Let me be very clear… Canada will always stand up for human rights in Canada and around the world, and women’s rights are human rights.”

The US on Monday asked for more information about the detentions. The United Nations has also expressed concern, and estimates that at least 15 Saudi activists have been arrested since May 15.

Saudi Arabia claims it’s targeting those who seek to “destabilize the Kingdom,” and claimed it was done as a counterterror measure. However, according to Human Rights Watch, many activists have remained in detention without being charged.